Wind energy is a clean and renewable energy resource, which is abundant all over the world, inexhaustible and environment-friendly. Wind power generation is therefore safe and clean, capable of providing a long-term and stable energy supply for mankind. Currently, most of major developed countries and developing countries have considered the development of wind power generation technology as their national policies and an important means to meet energy challenges in the new century. The mechanical transmission chain and electric transmission chain are core parts of a wind turbine generator system. As shown in FIG. 1, the mechanical and electric transmission chains of traditional MW wind turbine generator system mainly consist of a wind wheel, an accelerating gearbox, a generator and a converter. Due to fluctuation of wind speed, the rotational speed of the wind wheel is variable, after passing the accelerating gearbox, the rotational speed is increased while the torque is reduced, and the rotational speed is still not constant, once the varying rotational speed is input into the generator, the frequency of the current generated by the generator is also changing, and therefore a converter is needed for rectification to form a current with the desired frequency of the power grid for grid-connection.
Along with the continually increasing proportion of the wind power in the power grid, the wind power's influence on the power grid is gradually increasing, which raises higher requirements for grid-connection on the wind turbine generator system. Currently, the converter technology can't meet all the requirements for connecting electrical power to grid, and sometimes, an additional module needs to be added to meet the requirements on the low voltage ride-through, which increases the complexity of the system and reduces the reliability. With the development of the offshore wind power, higher requirements on the reliability of the wind turbine generator system are raised, and the reliability of high-power electric devices is a key factor restricting the development of the wind turbine generator system. Many organizations at home and abroad have studied on mechanical synchronizers, in an attempt to replace the converter of relatively lower reliability.
The existing mechanical synchronizers mainly are of two types: one is that a differential driving is conducted with the hydraulic torque converter feedback, although such a mechanism has good mobility, the manufacturing is complex, the accuracy requirement is strict, the cost is high and the efficiency of the hydraulic torque converter is low; the other is that the differential mechanism is driven to adjust the speed via a hydraulic servo or a servo motor, the hydraulic servo variable displacement pump or the variable displacement motor is of high cost and slow response, when a servo motor is used alone, there is a need to add a reducer, to increase the rotational inertia of the system, thus the starting and speed controlling performances of the system are inferior to the hydraulic system, the volume is larger and overload protection capacity is lower, and the flexibility is inferior to the hydraulic system.